Condenser



July 23, 1940 l.. G. KETCHAM 2,208,931

' coNDENsER Filed oct. 1a, 1935 2 sheets-sheet 1 INVENTOR, Bgm/72 ecfza//z Patented July 23, 1940 UNITED STATES PATENT oFFlcE 2,208,931 ooNDENsEB.

Application October 18, 1923.5, Serial No. 45,585

3 Claims.

'Ihis invention-relates to condensers for use in radio apparatus and particularly to condensers of the type known to the art as trimmer condensers utilized for making ne adjustments in the capacity of a circuit.

'I'his application is a continuation in part of my copending application Serial No. 743,716, led September 12, 1934.

An object of the invention is to provide a new,

l0 simple, eiiicient and inexpensive condenser of very small variable capacity.

Another object of the invention is to provide a condenser of such construction that the ca` pacity thereof can be varied by simply rotating a single control member.

A further object of the ,invention is to provide a condenser in which themovable plate is so constructed as to be forced away from the fixed plate normally under its own resiliency.

Another object of the invention is to provide a gang condenser assembly in which one member serves as, a plate common to all the condensers in the gang.

In carrying out the foregoing and other ob- I central aperture and with recesses in opposite -edges thereof. The lower plate of the condenser is provided with depending tongues to t in the recesses, and has an end portion cut away to register with the opening in the base but the cut away portion is of such size as not to contact with an eyelet passing through the opening in the base. The lower plate is provided with an aperture punched therefrom into the fashion of a burr, the walls of the aperture and of the burr being internally threaded. A strip of dielectric material is positioned on top of the lower plate.

` The upper plate` comprises a -fiat metallic portion adapted to lie over the dielectric material, such portion being joined to another portion of the plate by means of separated bowed connecting strips somewhat similar to those previously described. A part of the material between the strips is movedby punching and the remaining portion is apertured and such portion is separated from the dielectric by another insulator similar to the base. The parts of the assembly, namely, the base, the lower plate, the dielectric I iaterial, the insulator and the upper plate, are secured together by means of a single eyelet passing through the assembly and headed under the base and over the upper plate. The upper plate is provided with an aperture in alinement with the threaded aperture in the lower plate but of considerably larger diameter. A headed screw passes through the upper plate and through the dielectric into threaded engagement with the aperture in the lower plate. This screw is insulated from the upper plate by means of a washer, preferably made of the same insulating material as the base. By this arrangement, the upper plate can be forced downwardly into close contact with the dielectric, in which position `the condenser has its greatest capacity but at the same time when the screw is loosened the upper strip, due to the resiliency of the bowed connecting strips, moves away from the lower plate to decrease the capacity of the condenser. This upper plate can move away from the lower plate until the ultimate minimum capacity of the condenser/ is reached, which capacity amounts substantially only to the capacity determined by the air gap between the plates.

A plurality of condensers made in accordance lrwith the foregoing can be combined into. a gang and, if desired, this gang can be so constructed that a single plate is common to all of the condensers in the assembly. The number of condensers in the assembly may vary as occasion demands, and a gang so constructed serves ad` mirably in installations wherein a plurality of condensers each have one plate grounded. Thus by utilizing a common plate for all the condensers in the assembly a single ground connection to this common plate can be utilized for the entire assembly. The common plate will be provided with upstanding tongues to engage in one of the insulating blocks of each unit to accurately position lthe units relative to the plate.

Other features, objects, and advantages of the invention will lbecome apparent by reference to the following detail description read in the light of the accompanying drawings, wherein Fig. 1 is a. plan view of a single condenser embodying the invention;

Fig. 2 is an end view of the same device.

Fig. 3 is a side view thereof.

Fig. 4 is a view of the other end thereof.

Fig.v 5 is a section taken substantially on the line 5-5 of Fig. 1.

Fig. 6 is a plan view of a gang condenser assembly embodying the invention; and

Fig. 7 is a similar view partially fragmentary of a modied form of gang assembly.

Referring now to the drawings and particularly to Figs. 1-5 inclusive, a base I0 is'provided in the shape of a rectangular block of insulated material, preferably of some highly compressed ceramic material which is substantially nonhygroscopic. This block I0 is provided with a central aperture I I and is provided in the opposite ends thereof with recesses I2.

The lower plate of the condenser is made up of a strip of metal I4 having one end cut away as indicated at `I5 (Fig. 1). The legs I6 formed by cutting away a part of the strip have tongues I1 punched therefrom to extend downwardly and to t into the recesses I2. The plate I'4 is provided with an aperture I8 so punched therefrom as to provide a burr I9-which is internally threaded. 'I'he opposite end of the plate I4 is bent downwardly as at 20 to provide a terminal. This terminal 20 has an opening 2I therein to facilitate the attaching of conductors, and *if desired it is provided with notches 22 for the same purpose.

Positioned on top of the plate I4 is a strip of dielectric material 24. The strip of material is preferably made of high quality mica. The strip 24 is provided with an opening substantially in alinement with the opening I I in block I0 and with a second opening substantially in alinement with the aperture I8 in the lower plate. Positioned on top of the dielectric 24 and over the block I0 is an insulator25 which for purposes of convenience may be a duplicate of the block I0.

The upper plate of the condenser assembly is made up of. a metal strip having flat portion 26 overlying'the dielectric material and having an opening 21 therein substantially coaxial with the aperture IB. The opening 21, however, is of considerably larger diameter than that of the aper ture I8. The fiat portion 26 has ,extending from one end thereof a pair of separated bowed connecting strips 28. Between the connecting strips 28 and formed integrally therewith is an at\ taching portion 29 provided with an. aperture 30 in alinement with the openings in the block I0 and the insulator 25. Depending from the attaching part 29 is a terminal portion 3| having an aperture 32 and notches 33 for the attachment of conductors.

The block I0, plate I4, the dielectric 24, the insulator 25, and the attaching portion 29 of the top plate, are all locked together by means of a single eyelet 34 passing through the alined openings in the members and headed under the block I0, and over the attaching portion 29. The opening I5 in the plate I4 is of such size as to prevent contact of the plate I4 with the eyelet, the position of the plate I4 being determined by the engagement of the tongues I1 in the slots I2 of blockl I0. A headed screw 40 passes through the opening 21 in the plate 26 through theopening in the dielectric 24, into threaded engagement -with the wall ofthe threaded aperture .I8 in the burr I9. This screw 40 is insulated from the upper plate by means of a washer 4I preferably made of the same materialas the block I II, and the insulator 25.

With the parts assembled as shown, the'condenser may have its capacity varied by adjustment of the screw 40. When this screw is tightened the upper plate 26 is forced against the dielectric 24 to cause the condenser to have its greatest capacity, while when the screw is loosened, the upper plate moves away from the'lower plate and the dielectric due-to the resiliency of the bowed connecting strips. This plate can move away from the lower plate until the condenser has' a minimum capacity which capacity -in l,practice has been found to be the result almost entirely of the capacity of the air gap between the plates. Thus, the minimum range of substantially two micro-micro-farads is obtained.'

The recesses I2 may be located in the upper block 25 instead of in the lower block Ill if desired, in which event the tongues I1 will extend upwardly from the lower plate- I4 instead of downwardly as shown. Since the terminal flange 3| extends downwardly adjacent the edges ofthe blocks I0 and 25, this ange preventsturning of the upper plate about the eyelet' as an axis and also aids in' aligning the partsof the unit. The bowed connecting strips 28 being substantially semi-circular in form, cause the upper plate to move away from the lower plate in a manner, which, while not quite rectilinear in fashion, closely approaches being rectilinear. Thus, when the upper plate moves awayfrom the lower plate the movement is more or less uniform, and as the result of such movement, when the plates are in their most spaced apart position the unit has been found to have the absolute minimum capacity. ,v

In Fig. 6 a modification of the invention is I shown, such modification consists of a gang condenser assembly utilizing a single metallic plate which is common to each unit of the gang. In

this figure of the drawings, 50 indicates a metallic plate which is provided with upstanding flanges 5I spaced about portions of the boundary thereof to form tongues which seat in-.recesses ininsulator blocks of the various units. shown, the gang is composed of units indicated generally at 54, 55, 56 and 51. Each unit is constructed in the same fashion as the -unit shown in Figsfl to 5, inclusive, with the exception'that the plate 50 replaces the individual plates I4 which wouldbe present in four units made up as previously described. In these units the upper blockl is provided with recesses for the 4reception of the tongues 5 I which tonguesserve to definitely locate the units about the plate 5l) and to aid in holding theunits properly aligned. A number of openings 58 are shown in the plate 50 for the purpose of mounting the plate in some convenient position relative to the chassis of a radio set;

In the arrangement shown in Fig. 7, a metallic plate 60 of strip form is provided with a plurality of upstanding flanges 6I, which again pr vide,

tongues to-,seat in recesses in insulating blo of ,the condenser units associated with the plate.

These units are indicated generally at 64, 65, 66, 61 and 68. The number of units inthe assembly may vary as conditions require; in actual practice assemblies having been made up in various numbers of units from two upwardly. In this assembly the plate 66 is common to each of the units' 64 to 68, inclusive, replacing what would be the individual plates I4 of single units should a number of single units be arranged in gang fashion in other 'suitable manner.

The gang condenser assemblies shown in Figs.

In the form 6 and 7 are of especial utility in installations connected inthe circuit so that for all practical purposes the units of the gang can be adjusted independently .of each other so that each unit may have the desired capacity rating.

`accessi i While the aligning arrangement utilized for registering the blocks of insulating material with the lower plate have been described as consisting of tongues on the plate and recesses in the blocks, it is to be understood that other arrangements can be used. For example, any type of cooperating formations on the plate and on one or both of the blocks will suiiice.

From the foregoing it will be seen that the present invention, in the various` forms illustrated, provides a new, simple, efficient and inexpensive type of condenser of small variable capacity which on account of the non-hygroscopic qualities of the insulating material will retain a capacity setting in spite of atmospheric changes. It is to be understood that the invention is not to be limited to the illustrated embodiments, but

is to be limited only by the scope of the follow-` ing claims.

I claim:

1. In a trimmer condenser, the combination of a rigid metal base serving as one of the condenser electrodes, a ceramic block, said base having one end lying flat against one face of said block and interlocked therewith, a metal stripI passing through said lug, said block and said" base torigidly clamp said block between said strip and said base.

2. In a trimmer condenser, the combination of a rigid metal base serving as one of the condenser electrodes, a pair of blocks of insulating material, said base having one end interposed between said blocks and lying nat against one face of one of said blocks and interlocked therewith, a metal strip having one end in the form of a plate forming a cooperating condenser electrode with' the rst-mentioned electrode, the other end of said strip being bent at right angles to the first-mentioned end and joined thereto by a bowed portion, said other end having a struckout lug disposed against the outer face of one of said blocks, and means passing through said lug, said blocks, and said base to rigidly clamp said blocks, base and lug together.

3. In a trimmer condenser, the combination of a rigid metal base serving as one of the condenser electrodes, a pair of blocks of insulating material, said base having one .end interposed kbetween said blocks, and lying ilat against one face of one of saidblocks, the contacting surfaces of the end of said base and of one of said blocks having formations cooperating to interlock said base and said block, a metal strip having one end in the form of a plate Aforming a cooperating condenser electrode with' the rst-mentioned elec'- trode, the other end of said strip being bent at right angles to the first mentioned end and joined thereto by a bowed portion, said other end having a struck-out lug disposed against the outer' face of one of said blocks, and means passing through said lug, said blocks, and said base to' LYMAN G. KETCHAM. 

